The projects under investigation are as follows: (1)\cDNA and genomic clones for fibronectin have been isolated and are being analyzed. The sequence data provide information on the structure of several binding sites of fibronectin, and subcloning of segments in expression vectors is being used to study structure-function relationships. Alternative splicing of the transcript of a single gene gives rise to several distinct mRNAs encoding variant fibronectin subunits. (2)\Retrovirus vectors have been developed that allow the introduction and expression of cDNA and genomic DNA segments into mammalian cells. These vectors are being developed further and used to analyze a variety of questions. (3)\DNA sequences that confer ouabain resistance on sensitive cells have been cloned and are being analyzed to determine their relationship to the Na+/K+ ATPase or other ion transport molecules. (4)\The processing of the carbohydrate side-chains of glycoproteins and the possible biological roles of different forms of these side-chains are being analyzed. (5)\Studies are continuing on the distribution, structure, and function of microtubule-associated proteins in different cell types and states using methods for the direct analysis of cytoplasmic microtubules. These studies will lead to a deeper knowledge of proteins of the extracellular matrix surface membrane and cytoskeleton that is necessary for understanding how alterations in these are involved in oncogenic transformation. (V)